When finished, the new $100 million structure will link the Concourse C to Concourses A and B, and it will serve as home to all types of new restaurants, bars and shops for passengers.

"They're getting ready to lay this concrete here. They're finishing up the steel and putting up the roof next, and they they'll start laying this concrete," said Paul Wiedefeld, the airport's executive director.

Wiedefeld said the project will create a world-class, state-of-the-art concourse that will also accommodate long-term growth.

Wiedefeld said the project will create a world-class, state-of-the-art concourse that will also accommodate long-term growth.

"This is just much more open. You'll be able to look at concessions, look out to the airfield. It's just much brighter and the ceiling it much higher," Wiedefeld said.

Passengers can expect 8,500 square feet of new food and retail space (amenities), a refreshed observation deck, an expanded and refreshed Concourse C, a new and bigger nine-lane security checkpoint that, most importantly, links the A, B and C concourses via an airside connector.

"If you were on the A/B Concourse and you wanted to connect in C ,you have to go out through security and back in through security. So, this limits you having to go through security twice," Wiedefeld said.

This is a major project that includes 2 million pounds of steel, half an acre of glass and more than 40 miles of electrical wire, Melser said.

Airport revenue is funding the project, which should be completed by the summer with full operation just in time for the holidays.

Exclusive: Peek inside BWI Marshall's construction

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While holiday travelers pass through Baltimore-Washington International Thurgood Marshall Airport, it's what they couldn't see that's truly exciting.